Dust filtration bag and frame apparatus and method

ABSTRACT

Presented is an improved dust filtration unit of the type characterized by a filter bag having a plurality of pockets conjoined to a unitary opening, the opening having a collar that extends circumferentially around the opening, and a frame for supporting individual pockets and circumferentially supporting the opening. The improvement includes the frame having circumferential sidewalls with substantially vertical portions and top edges. A flange extends outwardly from the top edges to define a parameter and the filter bag includes an elastic hem at an outer edge of the collar. The bag is inserted within the sidewalls of the frame and the elastic hem edge of the collar is stretched over the flange for supporting attachment thereto.

TECHNICAL FIELD

This invention relates to an improved filter bag and frame combinationfor use in a compact self-contained dust collector in light industrialuse. In particular, the invention relates to the combination of amulti-pocket filter bag with a collar having an elastic hem that caneasily be stretched over a frame having an outwardly-extending flangefor secure attachment.

BACKGROUND OF THE INVENTION

An air filtering apparatus may take a variety of forms depending uponthe application for which it is intended. In industrial applications,the filtration unit typically includes a housing, sometimes referred toas a bag house, that is divided into two internal chambers: 1) a dirtyair chamber and 2) a clean air chamber. The two chambers are divided bya wall, known as a tube sheet, on which some type of filter media ismounted such that contaminated air is drawn by a fan into the dirty airchamber, through the filter media and openings in the tube sheet, to theclean air chamber. The filtered air is then either exhausted to theoutside atmosphere or recycled to the industrial work environment.

One popular form of filter medium is a plurality of relatively flat bagor pocket type filters positioned in a side-by-side relationship andsuspended from a frame. This type of filter provides maximal surfacearea through which the dirty air is drawn, allowing large amounts ofcontaminants to be collected prior to the filter media becoming clogged.Typically, the collection bag or pockets are occasionally shaken inorder to physically dislodge accumulated particulates so that they maybe collected for disposal and the useful life of the filter extendedbetween more thorough cleanings or replacement.

The principles of operation summarized above are described in U.S. Pat.No. 3,733,790, issued May 22, 1973, to Leo A. Pierce, the specificationof which is incorporated by reference herein. Several evolutionaryimprovements have been made to that apparatus, including improvements onhow the plurality of filter bags are assembled, mounted, and installed.For example, U.S. Pat. No. 4,323,376, issued Apr. 6, 1982, to Arthur P.Rosenquest discloses an improved filter bag construction in which theplurality of bags are unitarily formed, can be hung on a support frame,and lifted as a unit by means of a mechanical apparatus into sealingcontact with the tube sheet. Yet another means for addressing thesecurement of a filter bag to a frame is shown in U.S. Pat. No.6,740,142, issued May 25, 2004, to John M. Buettner, et.al.,specifically at FIG. 7. Another method for assembling and installing amulti-pocket filter bag on a support frame is described in U.S. Pat. No.5,931,988, issued Aug. 3, 1999, to LeBlanc, et al. These references arealso incorporated herein by reference and should be considered by thereader in order to put the present invention into proper context.

Another prior art design (which will be described in greater detailbelow) is shown in FIGS. 3, 4 and 5, herein. This design is presently incommon use. A plurality of bag pockets are conjoined to a single openingto form a filter bag unit. The opening has an extended collar ofmaterial that extends circumferentially around the opening. The bag issupported on a frame with an upwardly extending edge. The collar portionis folded over to an overlapping position on the outside of the frameand a retainer is inserted on the inner side of the frame, gripping aportion of the bag collar therebetween.

Each of the above-described embodiments, though improvements in theirown right over the original design, remain difficult for an untrained orunskilled person to properly assemble and position without engaging inmany frustrating attempts. Units in which this type of filter assemblyare used may be found in service in light duty situations, such as dustcollection for a high school or vocational school shop. In suchinstallations, it is often the building custodian, rather than aspecially trained technician, who is responsible for routine maintenanceand replacement of filter bag units. A simple, reliable and low costsolution for inserting and attaching the multi-pocket filter bag to theframe and insertion into position against the tube sheet is needed.

SUMMARY OF THE INVENTION

The present invention provides an improved dust filtration unit of thetype characterized by a filter bag having a plurality of pocketsconjoined to a unitary opening with the opening having a collar thatextends circumferentially around the opening and a frame for supportingindividual pockets and circumferentially supporting the opening. Theimprovements comprise the frame having a circumferentially flangeoutwardly extending from the frame to define a perimeter. The filter bagincludes an elastic or drawstring hem at the outer edge of the collarsuch that, when the bag is inserted within the frame, the hem edge ofthe collar may be stretched over the flange for secure supportingattachment thereto.

The outwardly extending flange provides a widened face against which thecollar can be engaged against an elastomeric gasket when installed inthe filtration unit. The frame may include substantially verticalsidewall portions having an upper or other edge from which thecircumferentially flange outwardly extends.

According to another aspect of the invention, it includes a method ofassembling a filter bag onto a support frame comprising the steps ofproviding a filter bag having a plurality of pockets conjoined to aunitary opening. The opening has a collar that extends circumferentiallyaround the opening and includes an elastic or drawstring hem at an outeredge of the collar. A frame is provided having a circumferential flangeoutwardly extending from an edge of the frame to define a perimeter. Thebag is inserted into the frame and the elastic or drawstring hem edge ofthe collar is stretched over the flange and drawn tight for supportingattachment thereto.

BRIEF DESCRIPTION OF THE DRAWING

Like reference numerals are used to denote like parts throughout variousfigures of the drawing, wherein:

FIG. 1 is a pictorial view of the external structure of a compactself-contained shaker-type dust collector in which the present inventionmay be used;

FIG. 2 is a partially cut-away pictorial view of the unit shown in FIG.1;

FIG. 3 is an exploded view of a prior art filter bag and frame assembly;

FIG. 4 is a partial, cross-sectional view taken substantially along line4-4 of FIG. 3 showing a detail of the assembled prior art frame and bagcombination;

FIG. 5 is a partially-disassembled pictorial view of the bag and framecombination of the prior art being inserted into its housing in the samemanner as the present invention;

FIG. 6 is an exploded pictorial view of the filter bag and framecombination of the present invention; and

FIG. 7 is a detail cross-sectional view taken substantially along line7-7 of FIG. 6 detail of a bag supported by a frame according to anembodiment of the present invention;

DETAILED DESCRIPTION AND BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the various figures of the drawing, and first to FIGS. 1and 2, therein is shown at 10 a typical compact, self-contained,shaker-type dust collection apparatus in which the present invention maybe used. A housing or cabinet 12 provides an enclosure divided into twointernal chambers: a dirty air or contaminated air chamber 14 and aclean air chamber 16. A blower or fan 18, typically powered by anelectric motor 20, may be positioned within or adjacent to the clean airchamber 16. An internal wall or partition, known as the tube sheet 17,separates the dirty and clean air chambers 14, 16. The fan 18 drawscontaminated air 22 through an inlet 24, into the dirty chamber 14, andthrough the filter media 26 which is sealed against the tube sheet 17.Access to the dirty air chamber 14 and the filter media 26 inside iscommonly had through a hinged door 28 on the front of the unit 10.Having particulate contaminants removed therefrom, clean air (shown byarrows 27 in FIG. 2) is drawn through the fan 18 and is either exhaustedout through the top of the unit to the outdoor atmosphere or may berecycled into the work environment.

The filtration apparatus 10 may also include a vibrating mechanism 30 ofwell known construction which, when the dust collecting apparatus is notoperating, mechanically dislodges heavy accumulations of particulatecontaminates (dust) from the filter media 26. After being shaken off thefilter media 26, the particulate contaminants fall by gravity into acollection chute 32 and further into a collection bin 34, which may beemptied as required.

Referring now to FIGS. 3, 4 and 5, as is well known in the prior art, afabric filter cloth bag 36 may be formed as a series of essentiallyu-shaped parallel folds with closed sides into which a relatively rigid,porous spacer material 38 is inserted. The filter bag 36 is theninserted into a rectangular frame structure 40 having upwardly-directedsidewalls 42 and a series of parallel rods 44 extended between oppositesides of the frame. Each fold 46 of the bag 36 forms a separate pocketand is held in position by the rigid spacers 38 and support rods 44. Inthis manner, the pockets are conjoined to a unitary opening having afabric collar 48 that extends circumferentially around the opening.

In the prior art design, the collar portion 48 of the bag 36 is foldedover the upwardly directed sidewall 42 of the frame 40 (see FIG. 4).After the collar 48 is folded over the outside of the frame 40, aretainer ring 50 is inserted within the frame 40 such that the collar 48is tightly clamped between the two frame parts 40, 50. Referringparticularly to FIGS. 3 and 5, the assembled filter media unit 26 isthen slid into the housing 12 onto a lifting mechanism 52 and, alongwith an elastomeric gasket 54, is lifted into sealing engagement withthe tube sheet 17. Although assembly of the bag 36 to the frame 40 inthis manner provides a secure attachment once the unit is in place,maintaining the collar 48 in place over the upwardly extending sidewall42 of the frame 40 while inserting the retainer ring 50 and moving theassembled unit into the housing 12 can be quite challenging for auntrained person servicing the unit 10.

Referring in particular to FIG. 4, it is readily seen that moving theretaining ring 50 downward (arrow 51) into position will inherentlycause the folded-over edge of the collar 48 to slip upward (arrow 53)and out of a secure position.

The present invention provides a simple and low cost solution to thisproblem. Referring now to FIGS. 6 and 7, therein is shown a preferredembodiment of the present invention. The pockets of the filter bag 136are formed in the typical way and receive rigid, porous spacer pieces138. The frame 140 includes the same type of support rods 144 extendingbetween opposite sides of the frame 140. The frame 140 differs, however,in that the sidewall 142, which can include an upwardly-extending,substantially vertical portion, has an outwardly extending flange 156.The flange 156 is preferably located at the top edge of the sidewall142, but may be at any position on the outer side of the frame 140. In apreferred form, the collar portion 148 of the bag 136 includes anelastic hem 158 that may be sewn onto the collar in the typical way thatan elastic cuff is formed in a sleeve, for example. Alternatively, thehem edge may include a manually retractable drawstring that can bepulled tight and secured in place over the flange 156.

In practice, the rigid spacers 138 are inserted into the pockets of thebag 136 and inserted into the frame 140 in the ordinary way. However,the collar portion 148 of the bag 136 is simply fitted over theoutwardly directed flange 156 by stretching the elastic or securing thedrawstring hem 158. The bag 136 and collar 148 are now securely held inplace without the need for a retainer ring (shown at 50 in FIG. 3). Theassembled unit is then easily insertable onto the lifting mechanism 52without risk of dislodging the collar 148 from its secure position onthe frame 140. A wide and smooth (not sharp) surface 160 is presented bythe assembled unit for sealing engagement against an elastomeric gasket(shown at 54 in FIG. 3).

The outwardly extending flange 158 can take any suitable form or be ofany width sufficient to cause the collar 148 of the bag 136 to remainsecure on the frame 140. Many other variations may be made to theillustrated and described embodiment without departing from the spiritand scope of the invention.

1. An improved dust filtration unit of the type characterized by afilter bag having a plurality of pockets conjoined to a unitary opening,the opening having a collar that extends circumferentially around theopening, and a frame for supporting individual pockets andcircumferentially supporting the opening, the improvement comprising:the frame having a circumferential flange outwardly extending from anedge of the frame to define a parameter; and the filter bag including aretractable hem at an outer edge of the collar; wherein the bag isinserted within the frame and the elastic hem edge of the collar isstretched over the flange for supporting attachment thereto.
 2. Theapparatus of claim 1, wherein the retractable hem edge includes elastic.3. The apparatus of claim 1, wherein the retractable hem edge includes adrawstring.
 4. The apparatus of claim 1, wherein the flange provides awidened face against which the collar can be engaged against anelastomeric gasket.
 5. The apparatus of claim 1, wherein the frameincludes substantially vertical sidewall portions having an edge fromwhich the circumferential flange outwardly extends.
 6. The apparatus ofclaim 5, wherein the circumferential flange outwardly extends from anupper edge of the substantially vertical sidewall.
 7. A method ofassembling an air filtration unit filter bag onto a support frame,comprising the steps of: providing a filter bag having a plurality ofpockets conjoined to a unitary opening, the opening having a collar thatextends circumferentially around the opening and which includes aretractable hem at an outer edge of the collar; providing a frame havinga circumferential flange outwardly extending from an edge of the frameto define a parameter; and inserting the bag into the frame andstretching the elastic hem edge of the collar over the flange forsupporting attachment thereto.
 8. The method of claim 7, wherein theretractable hem edge includes elastic.
 9. The apparatus of claim 7,wherein the retractable hem edge includes a drawstring.